1. Field of the Invention
This invention relates generally to an improvement in a loom equipped with a weft picking control system, and more particularly to the weft picking control system arranged to control weft picking in an optimum condition.
2. Description of the Prior Art
A variety of weft picking control systems of looms have been proposed to attain good weft picking. One of these is disclosed, for example, in U.S. Pat. No. 4,446,893 entitled "Method for Transporting a Weft Thread through the Weaving Shed of a Weaving Machine through the Intermediary of a Flowing Fluid, and Weaving Machine adapted for the Application of this Method". The weft picking control system in this U.S. patent is arranged as follows: A weft yarn is picked into the shed of warp yarns under the influence of tranporting fluid ejected from a plurality of nozzles, in which the transporting speed or time of the picked weft yarn is measured by detecting a timing at which the tip end of the weft yarn reaches an anti-weft picking side from a timing of starting of weft picking. The revolution speed of a main shaft of the loom or the transporting speed of the weft yarn is controlled in such a manner that the measured time occupies a predetermined fraction of time in a weaving cycle. This is effective for reducing mispick.
Now, if weft picking conditions are the same and weft yarns are the same in character, time periods required for weft pickings are theoretically the same. However, in practice, there arise differences in weft picking time periods among a plurality of weft pickings. In this regard, weft picking is not necessarily accomplished in a optimum condition even by controlling a fluid to be supplied to a weft inserting nozzle or by controlling the revolution speed of a main shaft of the loom upon comparing the weft picking time period for each pick with a standard value. In view of this, with the arrangement of the above-mentioned U.S. patent, the weft picking time periods of a plurality of weft pickings are averaged to obtain an average value, and the weft picking control is made in accordance with the average value, thereby preventing drawbacks due to the differences in weft picking time period among a plurality of weft pickings.
However, in such a weft picking control made in accordance with the average of a plurality of weft picking time periods, the control of the fluid to be supplied to the weft inserting nozzle or the control of the loom main shaft revolution speed cannot be carried out until a plurality of weft pickings are completed. Accordingly, even when a significant change in loom operation is made (for example, a weft package is changed to another one in which an empty winding state is changed to a full winding state thereby requiring a large weft picking force), the weft picking cannot be changed until a plurality of weft pickings have been completed, thus arises a shortage in weft picking forces which may lead to stopping of loom operation. This hinders effective weft picking control.
Otherwise, it has been proposed to make a similar control by obtaining, for each pick, an average value of a plurality of previous weft picking time periods assuming the present time as a standard. However, the speed of calculation is not high and therefore the control cannot follow the revolution of the loom, thus making it impossible to put it into practical use.